1. Field of the Invention
The present invention relates to an exhaust gas heat exchanger in which an internal fluid passage is formed by using plate-like members. Specifically, the present invention relates to thinning the thickness of the plate-like members which are disposed adjacent with each other.
2. Related Art
A Japanese Laid-open patent application No. 2001-41678, now which is matured to U.S. Pat. No. 6,401,804, discloses a heat exchanger, such as the one described above, which is formed by only using plural heat-exchanging plates defining an inside fluid passage without using a fin member such as a corrugated fin, while having a sufficient heat-transmitting performance, i.e., necessary heat-transmitting performance. In this heat exchanger, plural projection ribs are formed on the heat-exchanging plate members to constitute the inside fluid passage in which inside fluid flows, and the heat-exchanging plate members are disposed adjacent with each other to form a core for exchanging heat. Moreover, outside fluid (conditioned air) flows in a direction perpendicular to that of inside fluid flowing in the inside fluid passage. The projection ribs serve as a disturbance generator to disturb a straight line flow of the outside fluid.
The heat exchanger described above has a component employing a clad material formed by cladding an aluminum brazing material on an aluminum core material. Each component is laminated contiguously to adjacent components to form an assembled body. The assembled body is transferred to a heating chamber for brazing while being kept in the form of the assembled body by using a jig. Then, the components are soldered with each other to form an integrated assembly.
Since the projection ribs serve as the disturbance generator which causes improvement of the heat-transferring effect of the outside fluid, the necessary heat-transferring performance is obtained without providing the fins on the outside fluid side.
As mentioned in the above described publication, when connecting components by brazing with an aluminum material, the strength of material used for the components is generally lowered in relation to an annealing temperature while brazing. FIG. 1 shows a relationship between tensile strength/proof strength of Aluminum A1100-H material and the annealing temperature when the Aluminum material is used to manufacture the core material. As understood from FIG. 1, the tensile strength/proof strength is lowered when the temperature exceeds around 200–250° C.
Thus, the thickness of the material has been selected by taking into account the lowering of the strength due to the annealing temperature, so that the withstanding pressure thereof is secured. In other words, it is required that the heat-exchanging plate has a predetermined thickness to secure the withstanding pressure for the inside fluid passage.